Shot ball having excellent strength and wear resistance and method for manufacturing same

ABSTRACT

Disclosed is a shot ball having excellent strength and wear resistance. The shot ball according to an embodiment of the present disclosure includes, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chrome (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities.

TECHNICAL FIELD

The present disclosure relates to a shot ball and a manufacturing method thereof, and more particularly, to a shot ball used in a shot blaster for surface modification and a method of manufacturing the shot ball.

BACKGROUND ART

A shot blasting process used for surface modification is a method for finishing the surfaces of strips cleanly by injecting a shot ball stored in a hopper at high pressure onto the strips so that the shot ball injected at high pressure collides with the strips to remove a scale, rust, coating, etc. existing on the surfaces of the strips by a mechanical force. The shot blasting process requires a shorter working time than a sand blasting process using sand.

For this purpose, a shot ball is manufactured using a material such as cast iron and stainless steel. Particularly, in order to improve wear resistance, a shot ball is generally made of a hard structure.

However, the shot ball is damaged when used for a long time. In this case, the shot ball does not sufficiently show the effect of surface modification, and makes defects such as scratches or dents on the surfaces of products.

DISCLOSURE Technical Problem

Embodiments of the present disclosure provide a shot ball having excellent strength and wear resistance, capable of being less broken and less deteriorating during a shot blast process, and a method of manufacturing the shot ball.

Technical Solution

One aspect of the disclosure provides a shot ball having excellent strength and wear resistance, including: by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chromium (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of Molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities.

The shot ball may have a diameter within a range of 0.1 mm to 5.0 mm.

Another aspect of the disclosure provides a method for manufacturing a shot ball having excellent strength and wear resistance, including: quenching a molten metal including, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chromium (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of Molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities through an atomizing method.

The atomizing method may include at least one of water atomizing and gas atomizing.

When the atomizing method is performed, a cooling rate may be set to 30° C./sec or more.

Advantageous Effects

The shot ball according to an embodiment of the present disclosure may not cause phase transformation during cooling and have an austenite phase until room temperature so as not to have a hard structure that is relatively easy to be broken, resulting in an excellent strength and wear resistance.

Further, the shot ball according to an embodiment of the present disclosure may have an effect of further improving strength and wear resistance through work hardening when being repeatedly used as an austenite structure having both strength and toughness.

DESCRIPTION OF DRAWINGS

FIG. 1 is a picture showing a cross section of a shot ball according to an embodiment of the present disclosure.

FIG. 2 is a picture showing a microstructure of a shot ball according to an embodiment of the present disclosure.

MODES OF THE INVENTION

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following embodiments are provided to sufficiently transfer the technical concepts of the disclosure to one of ordinary skill in the art. However, the disclosure is not limited to these embodiments, and may be embodied in another form. In the drawings, parts that are irrelevant to the descriptions may be not shown in order to clarify the disclosure, and also, for easy understanding, the widths, lengths, thicknesses, etc. of components are more or less exaggeratedly shown. Like numbers refer to like elements throughout this specification.

A shot ball having excellent strength and wear resistance, according to an embodiment of the present disclosure, may include, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 1.0% to 8.0% of chromium (Cr), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), iron (Fe) and other unavoidable impurities.

The carbon content may be 0.09% to 1.3%.

Carbon is added as an essential element for securing the strength of a shot ball and stably forming an austenite phase, and 0.09% or more of carbon may be added. Also, wear resistance, which is a major performance factor of the shot ball, increases in proportion to a carbon content. However, when carbon is added excessively, brittleness increases. Therefore, the upper limit of a carbon content may be 1.3%. Therefore, a carbon content may be preferably limited to be more than 0.09% and equal to or less than 1.3%.

The manganese content may be 3.0% to 29%.

Manganese acts as an austenite stabilizing element and enhances the work hardening of the shot ball. Also, manganese contributes to the strength, impact toughness and wear resistance of the shot ball, so that 3.0% or more of manganese is added. Also, when a manganese content exceeds a predetermined content, the non-magnetic property is maintained even after processing. However, because manganese excessively added in a shot ball leads to deterioration in productivity and quality of the shot ball, a manganese content may be preferably limited to 3.0% to 29%.

The chromium content may be 1.0% to 8.0%.

Chromium is an element essentially added to produce carbides such as MC and M23C6, which increases high-temperature strength, and accordingly, 1.0% or more of chromium may be added. That is, when a predetermined amount of chromium is added, a high degree of precipitation hardening may be obtained, and furthermore, lowering an austenite stabilizing element content is possible. Therefore, 1.0% or more of chromium may be added. In addition, chromium is a strong anti-oxidation element and has an advantage of increasing oxidation resistance corresponding to an external oxidizing atmosphere. However, when chromium is excessively added, carbides may be excessively formed and an economical problem may occur. Therefore, an upper limit of chromium may be 8.0%.

The phosphorus content may be 0.05% or less.

Phosphorus is generally regarded as a hazardous element because of the possibility of secondary segregation in the solid phase. Therefore, it will be preferable that phosphorus is not used. However, in view of problems in steelmaking technology, a phosphorus content may be preferably limited to 0.05% or less.

The sulfur content may be 0.05% or less.

Sulfur tends to greatly reduce toughness in the transverse direction. Therefore, to obtain a shot ball having excellent impact toughness, it will be preferable that sulfur is not used. However, in view of problems in steelmaking technology, a sulfur content may be preferably limited to 0.05% or less.

The nickel content may be 10% or less (excluding 0).

Nickel forms austenite by solid solution strengthening, and has an excellent effect in improving toughness at low temperature. The addition of nickel promotes a formation of austenite to increase the toughness of the shot ball, thereby reducing the risk of breakage due to an impact during use. However, when a nickel content exceeds 10%, the toughness is greatly improved, but stacking fault energy (S.F.E) increases, thereby significantly lowering the wear resistance. In addition, adding a large amount of nickel is disadvantageous in view of economics due to its high price. Therefore, a nickel content may be limited to 10% or less (excluding 0).

The molybdenum content may be 7.0% or less (excluding 0).

Molybdenum is an element that may improve the strength of the shot ball through solid solution strengthening of a base. In addition, molybdenum acts as a major element causing precipitation hardening similar to niobium (Nb) and vanadium (V). However, molybdenum added excessively causes a deterioration of toughness and a remarkable increase of production cost. Therefore, a molybdenum content may be limited to 7% or less.

The tungsten content may be 10% or less (excluding 0).

Tungsten is an element that may improve strength by solid solution strengthening of a base. In addition, tungsten acts as a major element causing precipitation hardening similar to niobium (Nb), vanadium (V) and molybdenum (Mo). However, tungsten added excessively saturates the effect, causes a toughness deterioration, and significantly increases the manufacturing cost of a steel material. Therefore, a tungsten content may be limited to 10% or less.

Hereinafter, a method of manufacturing a shot ball having excellent strength and wear resistance, according to an embodiment of the present disclosure, will be described.

First, a molten metal including, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 1.0% to 8.0% of chromium (Cr), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of Molybdenum (MO), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities may be quenched through a gas atomizing method or a water atomizing method to produce fine grains. Herein, a diameter of a shot ball obtained by the atomizing method may be within a range from 0.1 mm to 5.0 mm. A cooling rate by the gas atomizing method or the water atomizing method may be set to 30° C./sec or more.

A cross section of a shot ball manufactured by this method is shown in FIG. 1, and FIG. 2 shows a cross sectional structure of the shot ball. As shown in FIG. 2, the cross sectional structure of the shot ball does not have a hard structure that is relatively easily broken, because it causes no phase transformation during cooling and has an austenite solidification structure until room temperature.

Hereinafter, the present disclosure will be described in more detail with reference to embodiments.

Table 1 shows wear resistance after a shot blast test using a shot ball which satisfies a component system and a composition range and is manufactured at a cooling rate of 30° C./sec or more by an atomizing method.

TABLE 1 Wear Specimen C Mn Cr P S Ni Mo W Fe resistance (%) inventive 1.15 18 2.8 0.02 0.01 4.5 6.8 9 Bal. 11 steel 1 inventive 1 17.5 2.4 0.02 0.01 5.2 6.2 8.5 Bal. 12 steel 2 inventive 0.5 18.9 2.7 0.02 0.01 7.3 5.9 9.7 Bal. 41 steel 3 inventive 0.1 15.4 2.8 0.02 0.01 6.8 6.3 9.2 Bal. 45 steel 4 inventive 1 22 2.1 0.02 0.01 7.2 6 8.4 Bal. 12 steel 5 inventive 1.05 29 2.4 0.02 0.01 7.6 6.5 8.8 Bal. 10 steel 6 comparative 0.05 17 2.7 0.02 0.01 5.2 6.1 8.9 Bal. 75 steel 1 comparative 1.02 1.5 2.3 0.02 0.01 7.5 6.2 8.2 Bal. 68 steel 2 comparative 1.1 18.2 10.2 0.02 0.01 6.8 6.2 8.1 Bal. x steel 3 comparative 1.15 17.8 9.5 0.02 0.01 6.2 5.9 8.2 Bal. x steel 4 comparative 1.12 17.9 0.2 0.02 0.01 6.5 6.4 8.1 Bal. 52 steel 5 comparative 1 18.5 2.6 0.02 0.01 12 6.1 7.5 Bal. 56 steel 6 comparative 1.05 18.2 2.5 0.02 0.01 6.2 10 7.9 Bal. x steel 7 comparative 1.02 18.9 2.8 0.02 0.01 7.5 6.2 15 Bal. x steel 8

Wear resistance: {(Particle size before test−Particle size after test)/Particle size before test}×100, and x indicates that particle evaluation is impossible due to breakage.

As shown in Table 1, it is seen that inventive steels 1 to 9 satisfying a steel component composition according to the present disclosure are excellent in wear resistance.

On contrary, it may be seen that comparative steels 1 to 8, which do not satisfy the composition of the present disclosure, show remarkable increases in breakage and wear resistance in the wear test.

Although a few embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 

1. A shot ball having excellent strength and wear resistance, comprising: by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chromium (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of Molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe), and other unavoidable impurities.
 2. The shot ball according to 1, wherein the shot ball has a diameter within a range of 0.1 mm to 5.0 mm.
 3. A Method for manufacturing a shot ball having excellent strength and wear resistance, comprising quenching a molten metal including, by weight %, 0.09% to 1.3% of carbon (C), 3% to 29% of manganese (Mn), 1.0% to 8.0% of chromium (Cr), 0.05% or less of phosphorus (P), 0.05% or less of sulfur (S), 10% or less (excluding 0) of nickel (Ni), 7% or less (excluding 0) of Molybdenum (Mo), 10% or less (excluding 0) of tungsten (W), the remainder iron (Fe) and other unavoidable impurities through an atomizing method.
 4. The method according to 3, wherein the atomizing method comprises at least one of water atomizing and gas atomizing.
 5. The method according to 3, wherein a cooling rate is set to 30° C./sec or more when the atomizing method is performed. 